Field of the Invention
The present invention relates to a lighting device which has an organic EL (electroluminescence) element as a light source.
Description of the Related Art
The organic EL element is capable of emitting light of high luminance at a low voltage, and various colors of the emitted light are obtained therefrom depending on types of organic compounds included in the organic EL element, and moreover, it is easy to manufacture the organic EL element as a planar light-emitting panel. As shown in FIG. 12, such a planar light-emitting panel 10 includes, for example, a base material 20, an organic EL element 30 provided in a center of the base material 20 and plural electrode pads 40 provided on the base material 20 so as to surround the organic EL element 30 (refer to Japanese Laid-Open Patent Publication No. 2012-182129, for example). Each of the electrode pads 40 is electrically connected to an anode layer or a cathode layer (neither of them is shown) of the organic EL element 30 and mediates a power feeding from an external power source to the anode layer or the cathode layer. In the planar light-emitting panel 10, a region corresponding to the organic EL element 30 is a light-emitting region 10A from which light is emitted and a region corresponding to the electrode pads 40 (shown by dots) surrounding the organic EL element 30 is a non-light-emitting region 10B from which the light is not emitted.
As shown in FIG. 13, the above planar light-emitting panel 10 can be utilized as a light source of a lighting device 50 which includes a housing 60 storing the planar light-emitting panel 10 and a translucent material 70 disposed on a light-emitting side of the planar light-emitting panel 10 (refer to Japanese Laid-Open Patent Publication No. 2011-108568, for example). The translucent material 70 and the base material 20 of the planar light-emitting panel 10 are adhered to each other with a translucent resin 80. Light emitted from the planar light-emitting panel 10 passes through the translucent resin 80 and the translucent material 70 and is emitted outside.
However, in the above lighting device 50, the front side of the light-emitting region 10A becomes a bright section emitting light of high luminance and the front side of the non-light-emitting region 10B becomes a dark section emitting light of low luminance, so that light irradiation region is small. Moreover, when the plural lighting devices 50 are arranged in a matrix form, the light irradiation surface does not become uniform where the bright section and the dark section are mixed, making the appearance of the lighting devices 50 awkward.